Mid-field plantings, balks – techniques, species selection – effectiveness in water retention

Balks and mid-field woodlots are an integral part of the field landscape associated with the diverse structure of crops and forms of ownership.

Mid-field woodlots have a fundamental impact on the preservation of the high biodiversity of arable land, due to their rich structure and wide variety of types. Spits are formed by narrow, uncultivated strips of grassy vegetation, marking the boundaries of fields, but also allowing safe communication, creating ecological corridors. Both types of sites, due to their location, the permanence of the vegetation cover, and the lack of mechanical and chemical human interference, participate in maintaining the biodiversity of the fields, providing valuable habitats for plants and numerous ecological niches for animals. They allow many predatory and parasitic insects and birds to breed, feed, overwinter and migrate, contributing to the control of crop pest numbers.

Maintaining a diversified agricultural landscape with plant cover in the form of balks and strip trees slows surface water runoff and, by filtering pollutants, improves ground and surface water quality. The tree canopies also create a favorable microclimate, weakening the force of the wind and increasing the humidity of the air.

Effectiveness of copper in conservation efforts

In order for spits to perform complex ecological functions, they must have certain physical characteristics. In large areas, the width of the fields should not exceed 100 m, and the width of the spits should not be less than 1 m. However, in the EU’s agri-environmental programs, in Package 8 (buffer zone), there is an emphasis on protecting even wider spit of land – 2- and 5-meter wide. Greater biodiversity is fostered by proximity to other natural habitats. The effectiveness of sodded buffer zones in water conservation depends largely on their design and width. The practice of leaving such zones is considered an effective form of reducing surface runoff (depending on conditions, it can range from 55 to 97%). Efektywność wąskich pasów do 5 m szerokości w zatrzymaniu biogenów jest bardzo zmienna i waha się w zakresie od 27-81% azotu oraz 15-96% fosforu, natomiast pasy strefy o szerokości 11 m są już bardzo skuteczne w wyłapywaniu zanieczyszczeń (75-98%).

Copper construction

The area of the spit is made up of a hump and an area of contact with the field. The vegetation cover on the elevated part is formed by permanent species, and in the lower part – at the interface with the field – by non-permanent plants. The older the spit is (as evidenced by a significant bulge), the richer it is in species. This relationship related to phytodiversity also applies to its width. The age of the spit can also be inferred from the type of vegetation: the predominance of dicotyledonous plants, especially perennials, testifies to a long-term process of succession in the area separating cultivated fields.

What plant species are found on the spits?

How many plant species can be found on the middens? The number of plants depends on the complexity of environmental and anthropogenic factors, ranging from <100, through> 100 or > 200 species. Phytodiversity is an important bee food source, especially during the period between flowering or after the harvest of cultivated species. Food sources for bees include plants with high honey yields, e.g. vetches, clovers, buttercups, and nostrums. If species poverty is observed, reseed segetal plants.

The spits are covered with a mosaic of species representing different ecological groups. The hump is dominated by species from meadow and ruderal habitats, and in the part of the interface with the field by segetal habitats. With the width of the area, the number of species preferring meadow habitats increases, and the number of “agrotolerant”, or segetal, species decreases. The grasses most often recorded there were perennial ryegrass, perennial couch grass, one-sided knapweed, common cocksfoot or raygrass. Of the dicotyledonous plants, white quackgrass, bird’s-foot trefoil, powdery mildew, common mugwort, and common nettle were numerous.

Spits provide sanctuaries for rare species of natural, semi-natural and segetal communities and enrich the network of functional links between ecosystems. Unfortunately, until the 1990s, farmers’ efforts were directed at eliminating weeds as competitors of crops. From the point of view of crop yields, complete elimination of weeds is not necessary under all conditions. Reducing weeds to a level that does not threaten economic crops and taking into account economic factors, allows to achieve the effect of protecting diversity.

What animal species are associated with the spit area?

The height-diverse vegetation cover (herbaceous plants, shrubs, trees), through its year-round presence, creates favorable conditions for the formation of ecological niches for animals residing temporarily or permanently in the fields. A large group of insects, birds or mammals are associated with the spit area. The closer to the spit, the more beneficial species were recorded, favorable in the fight against pests. A special role on the spit is played by trees or shrubs, with which small songbirds are associated (nightingale, pied-billed warbler, thorn-billed warbler, whorled warbler, potbellied warbler, reed warbler) that eat huge amounts of insects. That’s why activists of the “Polish Birds” Association appealed to farmers to leave balks in their crops.

Recommendations to preserve biodiversity on spits::

• do not plow the edges of the spit of land,
• do not apply chemical pesticides to field edges,
• leave at least 1 m width of the bellow,
• when using long-term monoculture crops or corn, use reseeding of segregated plants.

Effectiveness of introducing trees and shrubs in preserving biodiversity and maintaining water retention

Any planting plan for intramural tree plantings should be preceded by an analysis of local environmental conditions and should meet the tree planting needs of the area. Many of the planned functions can and should be combined, e.g., protection against water erosion with providing bees with food. Native tree and shrub species should be selected, preferably deciduous tree seedlings of good quality (with a covered root system). It is recommended that the proportion of deciduous species should be at least 90% and include at least 3 different species of trees or shrubs, with a minimum of 10% of at least one species and at least 20% of honey-giving species. Adequate species composition will help improve the biodiversity of the agricultural landscape. The form of mid-field plantings will depend on the expected function and location. In practice, the form used is the clump form (mid-field remixes), a line of trees and shrubs, tree canopies in the form of buffer zones, and agroforestry (agroforestry) systems.

Mid-field remotes are designed to provide conditions for mammals and birds to thrive. They are also important in protecting the water resources of the field. Detailed rules for the establishment of a remit can be found in AFINET’s brochure on remits at agrolesnictwo.pl.

Rows of mid-field trees shield from wind and water runoff and provide ecological corridors. These protective functions are influenced by: the height of the trees (it is recommended to use the lowest possible), the orientation with respect to the sides of the world (the direction of the prevailing winds), the distance between the rows (on light soils on average 250-300 m, and in the case of perpendicular barriers max. 600 m), the density of crowns and the coverage of sub-crown clearances (not too dense – about 20-30%, also with the participation of a shrub belt), the species of tree (e.g., oaks, ash, maples, lindens, poplars) and the type of soil. On slopes prone to water erosion, sodded strips 300 m long (with the participation of low shrubs) should be introduced in the upper part of short slopes or at intervals of no more than approx. 200 m on longer slopes.

Wooded buffer strips will best protect against leaching of minerals into the waters if the structure of the trees and shrubs is loose, and the species are adapted to moist habitats (e.g., black cherry, alders, willows).

Agroforestry systems involve the coexistence of trees/shrubs and agricultural crop or livestock production in the same area. Their main purpose is productive (timber / fruit / fodder) – they are most often: fruit trees, ash trees, maples, lindens, poplars. They also provide many soil and water conservation and biodiversity support services.

For more information, see the EcoDevelopment Foundation brochure edited by Kujawa et al. and agrolesnictwo.pl

In order to maintain the environmental functions of existing baulks or mid-field woodlots, good practices should be used to prevent their destruction, such as planting trees in place of fall-out also helps ensure the continuity of the benefits provided by the woodlots. Research from the Wielkopolska region has shown that in 8 years the total density of linear tree canopies has decreased by 9%, mainly due to the liberalization of their cutting in 2017. The role of baulks or strip tree plantings as pro-environmental areas cannot be overestimated, even if they account for 0.8% of the total area.

Literature:

1. Gamrat R., Gałczyńska M., Sotek Z., Stasińska M. 2018. Phytodiversity of midfield balks in a selected area in north-west Poland. Applied Ecology and Environmental Research 16(4), 4541-4558.
2. Kujawa A., Kujawa K., Zajączkowski J., Borek R., Tyszko-Chmielowiec P., Chmielowiec-Tyszko D., Józefczuk J., Krukowska-Szopa J. 2018. Zadrzewienia na obszarach wiejskich – dobre praktyki i rekomendacje. Fundacja EkoRozwoju, Wrocław.
3. Kujawa K., Janku K., Mana M., Choryński A. 2021. The loss of woody linear landscape elements in agriculture landscape in Wielkopolska region (Poland) in 21th century. Baltic Forestry, 27(1).
4. Skrajna T., Bogusz A. 2020. Floral diversity of plant communities in field balks. Studia Quaternaria 37, 1, 45-50.
5. Zajączkowski J., Zajączkowski K. 2013. Zadrzewienia. W: Hodowla lasu. PWRiL, Warszawa.

Authors:

Robert Borek – Institute of Fertilization and Soil Science in Puławy, Department of Bioeconomy and System Analysis

Renata Gamrat – West Pomeranian University of Technology in Szczecin, Department of Environmental Design

The text was written as part of the project „Hydrozagadka – jak wygrać z suszą?”